Cushioning mechanism for drop-heads of ballast displacing machines



Jan. 4, 1955 F. H. PHILBRICK 2,698,674

CUSHIONING MECHANISM FOR DROP-HEADS 0F BALLAST DISPLACING MACHINES Filed Feb. 4, 1952 5 Sheets-Sheet 1 I I I Jan. 4, 1955 F H PHILBRICK 2,698,674

CUSHIONING MECHANISM FOR DROP-HEADS 0F BALLAST DISPLACING MACHINES FiledFeb. 4, 1952 5 Sheets-Sheet 2 Jan. 4, 1955 F. H. PHILBRICK CUSHIONING MECHANISM FOR DROP-HEADS 0F BALLAST DISPLACING MACHINES 5 Sheets-Sheet 3 Filed Feb. 4, 1952 M ,r w

Jan. 4, 1955 F. H. PHILBRICK 2,698,674 CUSHIONING MECHANISM FOR DROP-HEADS 0F BALLAST DISPLACING MACHINES Filed Feb. 4, 1952 5 Sheets-Sheet 4 J22 J15 J04 1142 1955 F. H. PHILBRICK 2,698,574

CUSHIONING MECHANISM FOR DROP-HEADS 0F BALLAST DISPLACING MACHINES Filed Feb. 4, 1952 5 Sheets-Sheet 5 atented. Jan. 4, 1 955 CUSHIONING MECHANISM FonnRoP-rrE sor BALLAST DISPLACIING MACHlNES Frank H. Phiibrick, Evanston, Ill.

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.1 p t irritant tct iss=stl The invention relates to ballast displacing machines, for example, those which are used to remove ballast from the cribs between the ties.

One object of the invention is to provide a ballast displacing machine of the drop head type which includes a series of digging tools for displacing ballast from a crib with eflicient shock absorbing and arresting devices for the drop head which become effective when the re maining ballast in the crib is insuflicient to absorball the kinetic energy in the drop head.

In machines of the drop hammer type forimparting strokes to digging tools for displacing packed ballast from the cribs between ties of a railway track, the ballast resists the impact tools produced by the drop head and absorbs their kinetic energy until as the ballast is progressively displaced and the resistance progressivelydecreases When the crib has been evacuated to' the desired level, the drop strokes of the tools must be limited; and a desideratum is to provide limit and cushioning devices by which the excess kinetic energy will be absorbed to reduce severe impact or shock stresses on the machine structure and the tools.

Another object of the invention is to provide a machine of the drop head type with pneumatic shock absorbing devices combined with brake means which will absorb the excess kinetic energy of the drop head as the resistance of the ballast decreases and will limit the downstrokes of the head and tools relatively to the machine structure.

Another object of the invention is to provide efficient pneumatic shock absorbing devices for drop heads which are adapted for heavy work, with brake means for checking rebound which results from the pneumatic devices.

Other objects will appear from the detailed description.

The invention consists in the several novel features hereinafter set forth and more particularly defined by claims at the conclusion hereof;

In the drawings:

Fig. l is a front view of a machine exemplifying the invention, parts being shown in section, the drop head being shown in its raised position;

Fig. 2 is a section taken on line 22 of Fig. 4, the

rep head being shown in its lowered position;

Fig. 3 is a detail of the abutment on the drop head which is intermittently engaged by the continuously driven lifting chain;

P Fig. 4 is a longitudinal section taken on line 44 of Fig. 5 is a section of the valve mechanism for controlling the brake device in normal position;

Fig. 6 is a similar view of said mechanism in position for operating the brakes during the downstroke of the drop head;

Fig. 7 is a similar view of said mechanism in position for retaining the brakes set during the upstroke of the drop head; and

Fig. 8 is a diagrammatic view of the pneumatic and brake devices and the air connections for their operation.

The invention is exemplified with a machine including: a portable truck frame which is equipped with wheels 10 to travel on the rails c of a railway track, a motor and transmission gearing (not shown) for propelling the truck and for providing power for operating the ballast displacing tools. This frame comprises longitudinal beams 11, transverse beams 12 and 14, upright beams 13, and side plates 15 all rigidly secured together.

A Vertically movable cross head 16 functions as a drophead and has mounted thereon the ballast displacing tools.

This head 16 is usually of suflicient weight, for example 3600to 3000 lbs., to operate the tools for severe hammer blows to the ballast. Cross head 16 comprises plates 23 which are rigidly secured together and spaced apart by plates 22. The ballast displacing tools are pivotally movable on studs 40, which are supported in said plates 23. Lifting strokes are intermittently imparted to head b n stnw sh P Q ..PQQE Q PQYQHWQ i transverseshafts24"wl1'ich* isjournalled"o'ntlie truckf frame; a sprocket 30 fixed to shaft 24; sprocket chains 3:3v extending around sprockets 30; idler sprockets 36. which are carried by levers 37 which are fulcrumed on the truck frame, and rollers 38 on chains 33 which are adapted to engage and release abutments 39 fixed on head 16 for imparting alternate lifting strokes of the head and for releasing it for drop strokes. During their up; ward travel rollers 38 engage abutments 39 and at the. end of the upstroke, release abutments 39 for dropping head 16. Springs 4-2 are applied to the upper ends of rods which are pivoted to levers 37 for urging idler sprockets 36 to keep chains 33 taut. Drop head 16 is guided vertically in a guide and cam structure which comprises upright beams 17, cross beams 18 and 19 rigidly secured together by a plate 45, members 48 having their upper ends fixedly secured to cross beam 19, a plate 51 fixed to members 48, cross beams 51 and 52'fixed to plate. 51 and shoes 41 fixed to and connecting the lower ends of beams 17 and members 48. Drop head 16 extends between the side members 48 and up.- right beams 17.

Drop head 16 carries a series of pivotally movable tools a for digging into and progressively displacing the ballast in a crib transversely to one side of the track and an oppositely acting series of pivotally movable toolsb for displacing the ballast transversely to the opposite side of the track. These tools are pivoted at their upper ends on studs 40 which are supported between the plates 23 of drop head 16. The displacing tools are swung transversely during the drop strokes of head 16 and as the level of the ballast is progressively lowered by displacement from the crib, the angular displacement of the tools increases. Members 48 are provided with edges having upper straight portions and cam surfaces 57 below said straight portions, for pivotally shifting the tools on drop head 16.

One of each series of tools a and b is provided with an upstanding arm 55 which carries a roller 56 on its upper end. Rollers 56 ride on the straight upper portions of the edges of members 48 of the cam structure during the upper portion of the drop strokes of head 16 for holding the tools against pivotal movement and on cam surfaces 57 during the lower portion of the stroke of said head to pivotally swing the tools. Tools a are positively shifted by an arm 55 and cam abutments 59 between the tools respectively for positively swinging this series of tools transversely and outwardly so that the lower ends of the tools will displace the ballast transversely from the crib. Tools 19 are provided with similar coacting cam abutments 60 for positively swinging this series of tools by the roller 56 and an arm 55 on one of the tools b. The displacing tools of each set are transversely arranged to progressively displace the ballast from the central portion of the track to one side thereof. The three inner tools a and b are adapted to work in the crib to displace the ballast outwardly under the rails, and the outer tools of each series extend over and to the outer sides of a rail for moving the ballast beyond the ends of the ties. The tools swing inwardly by gravity during their idle up-stroke and are positively controlled during their down-stroke by arms 55, rollers 56 and cam surfaces 57. The lower end of each of the outer tools a and b is also guided by a roller 59 which is on a shoe 45. The guide structure is movable vertically inthe truckframe and guided by vertical rods 43 which are fixed in brackets 44 which are secured to beam 19 and plate 51 respectively, and are slidable in bearings 46 which are secured to upper and lower cross beams 14, respectively. Springs 48 between upper bearings 46 and collars on rods 43 yieldingly support rods 43 and the guide structure at its rear side. At its front side, the guide structure is yieldingly supported by compression springs 66 which surround rods 67. Springs 66 are seated on abutments 68 engaging brackets fixed on a cross beam 14. Rods 67 have their lower ends pivotally connectedto brackets fixed to upright beams 17, extend through the springs 66 and are provided at the upper ends with adjustable abutments 69 which bear on the upper ends of said springs. Shoes 41 are adapted to abut the upper face of the heads of rails c to transmit the down thrust stresses from the guide structure to the rails c when the drop head exerts downward stresses on the guide structure. Springs 48 and 66 hold the guide and cam structure raised when the drop head 16 is supported by the lifting rollers 38 on chain 33. During the portion of the strokes of head 16 when the rollers 56 for controlling the swinging of the tools, engage and exert a downward pressure on cams 57, the guide and cam structure will be lowered against the force of springs 48' and 16 until shoes 41 engage the track rails. When the drop head is in its raised position and supported by lifting rollers 38 shoes 41 will be lifted off the track rails by springs 48 and 66 for releasing the truck for travel to successive cribs. This guide and cam structure is also adapted to be raised for additional clearance between the shoes 41 and the track rails for extended travel of the machine on the tracks by a pair of pneumatic rams 7 which are supported on the'truck frame and are adapted to engage bridge plates 71 on beams 73 which are fixed to cross beams 12 and 19. When the rams are operated they will engage plates 72, lift the cam and guide structure and shoes 41 into their lifted position.

When drop strokes are imparted to head 16 and the displacing tools, the ballast will be progressively removed from the cribs in which the tools are operated and the length of the drop strokes and the angular movements of the tools will increase as the ballast is displaced.

The tools at the beginning of an operation in a filled crib are checked or retarded by the ballast. As the operation continues, the ballast is loosened and partially displaced from the crib, the tools swing outwardly in increasing angles, the resistance of the ballast to the tools decreases to such an extent that it is necessary to cushion and check the downward travel of the drop head during the later portion of the drop strokes, particularly as the level of the ballast is lowered approaching the completion of an operation in a crib. It is also advantageous to leave the drop head free for hammer effects of the tools during the initial portion of crib operation while the ballast offers the maximum resistance to the tools. For attaining these advantages, the invention provides pneumatic shock absorbing or cushioning devices between the drop head and the guide structure which remain ineffective during that portion of each drop stroke of the cross head while the maximum force is necessary to operate the tools to dig into the ballast and which become effective to limit the stroke of and retard the head during that portion of each drop stroke of the head when the resistance of the ballast is decreased to avoid imposing severe impact stresses on the machine structure.

Pneumatic devices are provided on the guide and cam structure and brake devices are provided between the drop head and upright beams 17 for limiting and cushioning the drop head as it approaches the end of its down strokes.

The invention utilizes air cylinders or dashpots and air operable brakes for cumulatively retarding or checking the drop strokes of the drop head and the air operated brakes for checking rebound during upstrokes of the drop head.

The devices for cushioning and limiting the movements of the drop head 16 comprises a pair of vertical cylinders or dashpots 80, each fixedly secured on one of the upright beams 17, a piston 81 slidable in each cylinder or dashpot 80 and a stem 82 fixed on each piston 81 and extending through and projecting above a head 83 on the upper end of said cylinder. The lower end of cylinders 81 is connected to receive air via a pipe 84, a valve 86 and a pipe 87 from a reservoir 85 in which a supply of compressed air is maintained at a predetermined pressure. Valve 86 is of the pressure-regulator type whereby air of higher pressure from reservoir 85 is controlled to supply air of a predetermined pressure, for example 70 p. s. i., to the pipe 87 and the lower ends of cylinders 80, and to maintain such a supply of air in cylinders 80 to replenish the air used from cylinders 80 in the operation 4 of the shock absorber system as hereinafter explained.

Abutments are provided on the drop head which are adapted to operate the pistons 81 downwardly in cylinder 80v against the predetermined air pressure normally maintained in the lower ends of said cylinder and to compress the confined air between the lower ends of the pistons 81 and cylinders 80 as the drop head continues its downstrokes after striking the piston stems 82. These abutments each include a bracket 90 fixed to drop head 16, a striker adapted to abut a stem 82, and a rubber cushion 92 interposed between bracket 90 and striker 91. These abutments are disposed on the drop head 16 so that they will engage stems 82 during a predetermined end portion of the drop stroke of head 16, for example 7" or 8". During this portion of the downstroke, the ballast is progressively displaced from the cribs and the necessity for absorbing shock occurs.

During this portion of the downstroke of head 16, the strikers 91 will operate stems 82 and pistons 81 downwardly in cylinders 80 and the air will be progressively compressed to the end of the downstrokes until it reaches, for example, 300 p. s. i. As a result, this air will retard the downward movement of the head 16 with progressively increasing pressure.

Air brake means are controlled by the drop head 16 through pressure developed in cylinders 80 to apply the brakes for retarding the downstrokes of head 16 for retardation supplemental to that of piston 81 and cylinders 80. This means includes a pair of brake shoes 94 on and carried by operating levers 95 which are fulcrumed at 96 on the drop head 16, an air cylinder 97 supported on levers 95, a piston 98 slidable in cylinder 97 and connected to one of the levers 95, a spring 99 for retracting the piston to release the brake shoes, and a flexible pipe 100 for supplying air to cylinder 97 for applying the brakes. Brake shoes 94 are adapted to engage fiat rails 101 which are secured to the confronting faces of upright beams 17. The brake shoes 94, levers 95 and cylinder 97 are movable vertically with the drop head so that when shoes 94 are applied to rails 101, the vertical movement of the drop head in its supporting structure will be frictionally retarded supplementally to resistance produced by air in the cylinders 80. The operation of the brakes is controlled by valve mechanism generally designated 103, which is controlled by the increase of air pressure in cylinders 80 during the downstrokes of pistons 81. Pipe 100 for delivering air into and exhausting air from brake cylinder 97 is connected to and controlled by said mechanism.

Mechanism 103 comprises a casing 104, a slide valve 105 in a chamber 106 which is communicatively connected by pipe 87 to the lower ends of cylinders 80, and controls the flow of air from chamber 106 via a port 107 in casing 104, a check valve 108 which controls the flow of air between port 107 and a chamber 109 in casing 104 to which air brake pipe 100 is connected. Valve 105 also controls the exhaust of air from brake cylinder 97 to air exhaust port 110. Valve 105 is operated by a stem 111 which is slidable in casing 104 and a piston 112 which is slidable in a cylinder 113 in casing 104 and is responsive to air of predetermined pressure admitted into cylinder 113 from a branch 114 of pipe 87. A spray 115 retracts the piston 112 when the pressure drops in cylinder 113. Check valve 108 is mounted on a stern 116 which is slidable in the casing 104 and extends into the cylinder 114. A spring 118 is applied to stem 116 for urging check valve 108 into its closed position until there is a predetermined pressure drop in chamber 106 and duct 107. Stem 111 for piston 112 is provided with an abutment 119 for engaging an abutment 120 on the stem 116 of check valve 108 to open said check valve when there is a predetermined pressure drop in the right hand end of cylinder 113 and in the lower portion of cylinder 80. In practice, it is desirable to vary the resistance to the outstroke of piston 112 for regulating the operation of piston 112 and the brakes responsive to different predetermined pressures in the cylinders 80. For this purpose, a pipe 122 is connected to the supply reservoir 85 and to cylinder 113 at the spring loaded side of piston 112 and an adjustable pressure regular valve 123 is included in said pipe. By adjusting the valve 123 to increase or decrease the pressure against piston 112 the predetermined pressure from cylinders 80 at which valve 105 is shifted to deliver air into air brake cylinder 97, may be varied.

The operation willbe: as follows: The machine will be spotted along the. railway track so that; the toolsa and b will be operable in a crib. Alternate lifting and drop strokes Wlll be imparted to head 16. During said drop strokes rollers 56 on tools a and b will engage camv surfaces 57 and force the cam. and guide structure downwardly until shoes 72 engage therailway rails c. During the lifting strokes of the head 16, rollers 38 will engage abutments 39 on said head which will bethen supported by chains 33. During the upper portion of the upstrokes of head 16, rollers 56 onv levers 55 will ride on the upper straight members 48 and springs 42 and 66 will lift the guide and cam structure and raise shoes 72 d the track rails c.

When the crib is filled with ballast, thetools a and b will progressively dig and. displace the ballast from the crib during the last portion of each downstroke of the head 16, and the ballast will absorb kinetic energy from said head. As the ballast. is. progressivelydisplaced, its level is lowered and the drop strokes increase in length, the angular movement of the tools is also increased in magnitude and the kinetic energy absorbed by the ballast progressively decreases. As the ballast in the crib is removed, the angular movement of the tool is increased and the ballast is deflected laterally; The bending stresses on the tools are severe Without adequatechecking and cushioning of the drop head. For this purpose the checking and shock absorbing devices become operative with progressively increasing efiect during a predetermined end portion of the downstroke of the head. Be-' fore that, the drop head is free to dropand develop kinetic energy for operating the tools, for example, 8" of the end of its downstroke. As the ballast is progressively displaced from a crib, the drop stroke of head 16 and tools a and b is increased and striker 91 on-said head will engage stems 82 on pistons 81 in cylinders 80 in which a predetermined air pressure, for example, 75 p. s. i. is maintained from reservoir 85 through pressure regulator valve 86. As the stroke of pistons 81 increases, the pressure in the lower ends of cylinders increases progressively until said pressure is increased, for example, to 300p. s. i. when a full stroke is imparted to pistons 81. During this increase of pressure, kinetic energy from the drop head will be absorbed by the air pressure in the lower ends of cylinders 86 to cushion and arrest the downstroke of the tools. When the maximum pressure is reachedin cylinders 84), it will be sulficient to support the static load and absorb excess kinetic energy at the end offull drop strokes.

While pistons 81 are in normal position and' the drop. head 16 is raised, air pressure corresponding to the same air pressure in cylinders 80, (for example 75 p. s; i.), will be maintained in cylinder 113 and chamber 106 of valve 104, and piston 112 will be held in the position shown in Fig. by spring 115. Slide valve 105 will out 01f the flow of air from chamber 106 to port 107, the pipe 100 and brake cylinder 97. Stem 111 engages stem 1 16 of check valve'108 and holds check valve 108 open against the force of spring 118. Piston 98 in cylinder 97 will be retracted by spring 99 and the brake shoes 94 will be disengaged from rails 181. During the downstroke of the drop head 16 the pistons 81 are operated and increase the pressure in cylinder 80 to a predetermined degree. The air resistance to the drop head is supplemented byretarda'tion by the brakes when the pressure in the right hand end' of cylinder 113 is correspondingly increased to preponderate the resistance of spring 115 and the limited air pressure in the left hand end of cylinder 113. When that occurs piston 112, stem 111 and valve 105 will be shifted to the position shown in Fig. 6. Air underpressure will then pass from cylinders 80 via pipe 114, chamber 106, port 197 and pipe 100 to the brake-cylinder 97, and operate piston 98 to shift levers 95 and apply the brake shoes 94 to rails 101. The brakes will then frictionally retard the downward movement of the head 16 and the tools a and. b. while the air pressure in cylinders 80 simultaneously checks and cushi ns the drop head as it approaches the end of its downstroke. During the initial portion of the succeeding upstroke of the drop head 16, strikers-91 move upwardly and release the stems 82 and pistons 81. The: air in cylinders 80 will expand during the upstroke of pistons and reduce the pressure in the right hand end of cylinder 113 against piston 112, so that-spr-ing1115 and thelimited air pressure in the left hand end of cylinder will shift piston 112 towards, its: normal position shown.

6 in Fig. 5. In transitto' its normal-position, piston 112 willi shift valve to exhaust air from duet 107, through exhaust port as shown in Fig. 7'. As the pressure dropsin duct 107,- spring-113 will closecheck valve-108 andretain the pressure in brakecylinder 97 for holding the brake shoes set. As the pistons 81 approach the end of their upstroke, abutment 119 engages abutment 1-20 on' stem 116 and opens check valve 106' against theforce of spring. 118 so that air will be exhausted from brake cylinder 97 via pipe 100, port 107, valve 105'and exhaustport 119, and spring 99 will retract piston 98 and operate levers 95 to release the brake shoes. Asa result of this construction and operation, the brake shoes will remain elfective to check upward rebound of thedrop head duringa predetermined initial portion of the upstroke of the drop head and while the pistons 81 are moving upward in cylinders 80 and pressure is dropping in cylinders 80 and the right hand endof cylinder 113 to the normal. in each operation of the pistons 81 and piston 98 causes a loss of air by the exhaust from the brake cylinder 97 to atmosphere. This produces a pressure drop in pipe 87 until the pressure regulated feed valve 86 opens and" admits sufiicient air to cylinders 80 tothe normal pressure (for example 75 lbs.) in said cylinders and cylinder 113; for initiation. of the succeeding operation of the brakes and the pistons 81 for the next downstroke of head 16- and tools a and b. By adjusting the valve 123, the pressure of air at the left side of cylinder 113 which supplements spring in resisting movement of piston 112-, can be varied to vary the predetermined pressure required toshift valve 105 for supplying air to the air brake cylinder 97, and the timing of the air brake during the downstroke imparted to pistons 81 by striker 91 on the drop head 16.

This construction exemplifies pneumatic devices with coacting brake devices for cushioning and arresting the drop head and tools thereon when approaching the end of each downstroke and checking rebound of the drop head and tools thereon during commencement of the upstroke; with the result that smoothness in operation. is achieved with a heavy duty drop head. The combined efiect of the pneumatic devices and the brakes is utilized while the greatest angular movement of the tools occurs duringthe displacement of the last portion of the ballast from the crib. This pneumatic return action of the crosshead from the position of greatest angularity of the digger members where the cam friction of the digger membersis the greatest, very materially assists the crosshead lifting chains in raising the digger head assembly from rest without shock;

The invention is not to be understood as restricted to the details set forth since these may be modified within the scope of the appended claims without departing, from the spirit and scope.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

1. Apparatus for cushioning the strokes of a power lifted drop head provided with tools for impacting ballast, comprising: a supply of air under pressure, cylinders mounted on the structure, pistons in the cylinder, each provided with a stern projecting from theupper end of a cylinder, abutments on the head for engaging the stems and operating the pistons in the cylinders during the end portion of the drop strokes and operable from the stems during upstrokes of the drop head, means for supplying a air pressure'from said source under a predeterminednressure into the lower end of the cylinders, the pistons being operable by said abutments to progressively increase the pressure of air in the lower ends of the cylinders for absorbing kinetic energy from the drop head. and means controlled by such increase of pressure for checkin rebound of the drop head during the initial portion of the upstroke of the head.

2. Apparatus for cushioning the strokes of a n wer. lifted drop head provided with tools for impactin ballast, comprising: a supply of air under pressure, cylinders mounted on the structure, pistons in the cylinders. each provided with a stem proiecting from the upper end of the cylinder, abutments on the head for enga ing the stems and operating the pistons in the cylinder during the end portion of the drop strokes, means for supplying'airpresr sure from said source under a predetermined pressure into the lower end of the cylinder, the pistons being operable by said abutments to progressively increase the pressure of air in the lower end of the cylinder forabsorbin'g-ltinet'ie' energy from the drop head,.and1 means controlled by the pistons for checking rebound of the head during the initial portion of the upstrokes.

3. Apparatus for cushioning the strokes of a power lifted drop head provided witn tools for impacting ballast, comprising: a supply of air under pressure, cylinders mounted on the structure, pistons in the cylinders, each provided with a stem pro ecting from the upper end of a cylinder, an abutment on the head for engaging the stem and operating the piston in the cylinder during the end portion of the drop strokes, and separable from the stems during their upstrokes, means for supplying air of a predetermined pressure from said source under a predetermined pressure into the lower ends of the cylinders, the pistons being operable by said abutment to progressively increase the pressure of air in the lower end of the cylinder for absorbing kinetic energy from the drop head, and means controlled by such increase of pressure for retarding the downstroke of the head and checking rebound during the initial portion of the upstroke of the head.

4. Apparatus for cushioning the strokes of a power lifted drop head provided with tools for impacting ballast, comprising: a supply of air under pressure, a cylinder mounted on the structure, a piston in the cylinder provided with a stem projecting from the upper end of the cylinder, an abutment on the head for engaging the stem and operating the piston in the cylinder during the end portion of the drop strokes, means for supplying air from said source under a predetermined pressure in the lower end of the cylinder, the piston being operable by said abutment to progressively increase the pressure of air in the lower end of the cylinder for absorbing kinetic energy from the drop head, brake means for checking the movement of the drop head, and means controlled by said increase of pressure for controlling the brake means.

5. Apparatus for cushioning the strokes of a power lifted drop head provided with tools for impacting ballast, comprising: a supply of air under pressure, a cylinder mounted on the structure, a piston in the cylinder provided with a stern projecting from the upper end of the cylinder, an abutment on the head for engaging the stem and operating the piston in the cylinder during the end portion of the drop strokes, means for supplying air from said source under a predetermined pressure in the lower end of the cylinder, the piston being operable by said abutment to progressively increase the pressure of air in the lower end of the cylinder for absorbing kinetic energy from the drop head, brake means for checking the movement of the drop head, and means controlled by said increase of pressure in the cylinder for applying the brake means during the end portion of the down stroke and the initial portion of the upstroke of the head.

6. Apparatus for cushioning the strokes of a power lifted drop head provided with tools for impacting ballast, comprising: a supply of air under pressure, a cylinder mounted on the structure, a piston in the cylinder provided with a stem projecting from the upper end of the cylinder, an abutment on the head for engaging the stern and operating the piston in the cylinder during the end portion of the drop strokes, means for supplying air from said source under a predetermined pressure in the lower end of the cylinder, the piston being operable by said abutment to progressively increase the pressure of air in the lower end of the cylinder for absorbing kinetic energy from the drop head, brake means for checking the movement of the drop head, and valve mechanism controlled by such increase of pressure in the cylinder for rendering the brake effective during the portion of the downstroke and the initial portion of the upstroke.

7. Apparatus for cushioning the strokes of a power lifted drop head provided with tools for impacting ballast, comprising: a supply of air under pressure, a cylinder mounted on the structure, a piston in the cylinder pro vided with a stem projecting from the upper end of the cylinder, an abutment on the head for engaging the stern and operating the piston in the cylinder during the end portion of the drop strokes, means for supplying air from said source under a predetermined pressure into the lower end of the cylinder, the piston being operable by said abutment to progressively increase the pressure of air in the lower end of the cylinder for absorbing kinetic energy from the drop head, air brake means mounted on the drop head and applicable to the structure for checking the drop head, and valve mechanism controlled by the pres- '8 sure in the cylinder for delivering air to said brake means to retard the movement of the drop head.

8. Apparatus for cushioning the strokes of a power lifted drop head provided with tools for impacting ballast, comprising: a supply of air under pressure, a cylinder mounted on the structure, a piston in the cylinder provided with a stem projecting from the upper end of the cylinder, an abutment on the head for engaging the stem and operating the piston in the cylinder during the end portion of the drop strokes, means for supplying air from said source under a predetermined pressure into the lower end of the cylinder, the piston being operable by said abutment to progressively increase the pressure of air in the lower end of the cylinder for absorbing kinetic energy from the drop head, air brake means mounted on the drop head and applicable to the structure for checking the drop head, and valve mechanism controlled by the pressure in the cylinder for delivering air to said brake means to retard the movement of the drop head and for exhausting air from the brake means.

9. Apparatus for cushioning the strokes of a power lifted drop head provided with tools for impacting ballast, comprising: a supply of air under pressure, a cylinder mounted on the structure, a piston in the cylinder provided with a stem projecting from the upper end of the cylinder, an abutment on the head for engaging the stem and operating the piston in the cylinder during the end portion of the drop strokes, means for supplying air from said source under a predetermined pressure into the lower end of the cylinder, the piston being operable by said abutment to progressively increase the pressure of air in the lower end of the cylinder for absorbing kinetic energy from the drop head, air brake means mounted on the drop head and applicable to the structure for checking the drop head, and valve mechanism controlled by the pressure in the cylinder for operating the brake means to check the drop head during the end portion of the downstroke and during the initial portion of the upstroke of the drop head.

10. Apparatus for cushioning the strokes of a power lifted drop head provided with tools for impacting ballast, comprising: a supply of air under pressure, a plurality of cylinders on the structure, pistons slidable in the cylinders. each provided with a stem projecting from the upper end of a cylinder, abutments on the head for engaging the stems and operating the pistons during the end portion of the drop strokes, means for supplying air of a predetermined pressure from said supply to the lower ends of said cylinders, the pistons being operable to progressively increase the pressure of air in the lower ends of the cylinders for absorbing kinetic energy from the drop head, air brake means for checking the movement of the head and means controlled by the pressure in the cylinders for controlling the operation of the brakes.

11. Apparatus for cushioning the strokes of a power lifted drop head provided with tools for impacting ballast, comprising: a supply of air under pressure, a plurality of cylinders on the structure, pistons slidable in the cylinders, each provided with a stem projecting from the upper end of a cylinder, abutments on the head for engaging the stems and operating the pistons during the end portion of the drop strokes, means for supplying air of a predetermined pressure from said supply to the lower ends of s id cylinders, the pistons being operable to progressively increase the pressure of air in the lower ends f the cvlinders for absorbing kinetic energy from the drop head, air brake means for checking the movement of the head. and valve mechanism controlled by the pressure in the cvlinders for supplying air to the brake means for its operation to check the head during the end portion of its downstroke and during the initial portion of the upstroke.

12. Apparatus for cushioning the strokes of a power lifted drop head provided With tools for impacting b llast, comprising: a supply of air under pressure, a cylinder mounted on the structure, a piston in the cylinder provided with a stem projecting from the upper end of the cylinder, an abutment on the head for engaging the stern and operating the piston in the cylinder during the ultimate portion of the drop strokes, means including a pressure regulated valve for supplying to and retaining air of a predetermined pressure from said source, in the lower end of the cylinder, the piston being operable to progressively increase the pressure of air in the lower end of the cylinder for absorbing kinetic energy from and supporting the static load of the drop head, air brake means for checking the head and galve mechFnisgllcontrolled bydthifiaressure in tPe cylililr References Cited in the file of this patent er, valve or e ivering to an e austing air rom t e brake means, a check valve for retaining air in the brake UNITED STATES PATENTS means, and a piston responsive to pressure in the cylinder 2,082,594. Philbrick June 1, 1937 for opening the check valve to exhaust air from the brake 5 2,309,712 Philbrick Feb. 2, 1943 means. 

